Since at least as early as the year 1906, devices permitting the sequential display of a plurality of coded images by relative movement of an image member relative to a shutter member have been known to the art. Based on the nature of their operation, such devices may be termed moveable display devices.
Most basically stated, such moveable display devices comprise an image member slidably retained adjacent to a shutter member. The image member has a plurality of interposed coded images disposed thereon. One looking at the image member separated from the shutter member would see the plurality of interposed coded images as apparently incoherent narrow strips or, possibly, dots, and the coded images would not be likely to be dearly cognizable.
The shutter member has a plurality of ideally opaque shutter elements disposed thereon that are separated by a plurality of translucent, ideally transparent, viewing elements. Certainly the prior art has made dear that the plurality of shutter elements may assume a wide variety of shapes including straight bars, curving bars, apertured opaque portions, and any other functioning configuration. Naturally, the shapes of the coded images would correspond to the shapes of the shutter elements. The plurality of viewing elements could comprise open slots, transparent bars, or any other means that would allow a selective viewing of the coded images.
It is worth noting that it is most common for the plurality of shutter elements to comprise straight opaque bars of ink or the like printed on a transparent substrate and for the plurality of viewing elements to comprise interposed portions that are devoid of ink. Accordingly, the present discussion will continue under the assumption that the shutter elements and the viewing elements are so formed but with the proviso that such need not necessarily be the case.
In intended operation, the plurality of shutter elements perform dual, equally critical functions. By their opaque nature, the shutter elements selectively block from view all but one of the plurality of interposed coded images. Accordingly, the image that is not blocked may be termed an active image. Just as importantly, however, the plurality of shutter elements bridge the gaps between the coded strips that comprise the active image. With this, the plurality of shutter elements uncode the active image of the plurality of coded images, and the active image appears to be complete.
When the image member and the shutter member are moved relative to each other a predetermined amount, the strips of the previously active image are concealed, and the next succeeding coded image assumes the fleeting position as an active image. This procedure will continue through a cycle comprising the number of coded images that are disposed on the image member whereupon the first coded image will again appear thereby signaling the start of a new, identical cycle.
The very astute observer will realize that the number of coded images that a moveable display device is able to display in a cycle is mathematically limited by the width of the shutter element relative to the width of the strips that comprise the coded images. Stated more particularly, the number of coded images cannot exceed one plus the result of the width of each shutter element divided by the width of each strip of the coded images. In the aforedescribed formula, the number one represents the active image while the result of dividing the width of each shutter element by the width of each strip of the coded images represents the number of images concealed by the shutter elements at any one time.
For a number of obvious reasons, there has been a recognized and long felt need in this art to provide a moveable display device that is capable of displaying an increased plurality of images. In light of the simple formula set forth above, it is readily apparent that an increase in the number of displayed images can be accomplished by increasing the number of the plurality of coded images concealed behind each individual shutter element, or, more specifically, by increasing the number of coded image strips concealed behind each individual shutter element.
To conceal an increased number of coded image strips behind each individual shutter element, one might increase the overall width of each shutter element. However, to maintain a display of relatively high image resolution, one widening each shutter element would be required to increase the physical size of the display itself. In most cases involving hand held moveable display devices, increasing the size of the display device would be impractical
Therefore, to increase the number of displayed images while maintaining an image of high resolution in a display device of a preferred physical size, it is preferable instead to narrow the overall width of the coded image strips while substantially maintaining the original width of the concealing shutter elements. Unfortunately, however, this preferred solution presents a plurality of practical problems at least in part because it necessitates that the width of the viewing elements be proportionately narrowed.
For example, a narrowing of the viewing elements results in a proportional increase for the need for precise registration between the coded images and the shutter elements, including during relative movement therebetween. In other words, where the strips of the coded images are very narrow, even a slight misalignment will destroy the device's ability to display coherent images. Furthermore, as the width of the strips narrows, the need for maintaining the coded images and the shutter elements in dose contact over their entire surfaces also increases proportionally. With very narrow strips of the coded images, even a very slight gap between the coded images and the shutter elements would ruin the clarity of the displayed images except from a perfectly perpendicular viewpoint, and even then true clarity might require that a user view the display device using only one eye.
For many decades, maintaining precise registration and dose contact between the shutter elements and the coded images in image display devices has been a recognized need and an explicit goal of a multiplicity of inventors. However, the proposed solutions of these inventors have proven to be undesirably complex, cumbersome, and, in some cases, of dubious effectiveness.
Relative to manually operated display devices, the inventor W. S. Russell recognized this need. In U.S. Pat. No. 1,259,297 for a Picture Display Holder, which issued in 1918, Russell attempted to provide a means for registering the shutter elements and the coded images in the form of gage marks on the shutter member and the image member that a user was expected to maintain in accurate registration merely by finger pressure. One must suspect that such a registering means would be vulnerable to misalignment particularly during movement, even with relatively wide coded image strips. Such limitations have continued to limit the number of images that manually operated moveable display devices are able to display effectively. Consequently, it appears that even in the most well made devices it has proven impracticable to display any more than four images effectively.
The need for accurate registration and close contact between coded images and shutter elements again was attempted to be addressed in the 1961 U.S. Pat. No. 3,000,125 to Elvestrom for a Pictorial Display Device. In that patent, Elvestrom revealed a complex arrangement of brackets and an adjustable nut and screw combination for maintaining and adjusting the alignment of his shutter elements and coded images. After describing this complex arrangement in detail, he writes, "Only a moderate amount of experimentation is required to achieve this desired setting." Without speaking to the effectiveness of the device, it must be said that requiring such a complex arrangement and the active involvement and expertise of a user certainly is less than ideal.
Still another attempt to provide a moveable display device that maintains full surface contact and accurate registration of a shutter member relative to an image member is found in the 1975 U.S. Pat. No. 3,862,504 to Ringelheim, deceased, et al. for a Visual Display Apparatus. In a telling manner, the patent declares tat, "the inability to maintain precise alignment" of the shutter elements and the coded images is a problem that has interfered with the commercial adoption of moveable display devices. Ringelheim also laments the need for maintaining close surface contact between the surfaces of the shutter member and the image member in moveable display devices. Having said these things, the inventor goes on to disclose a complex coil spring and cam follower arrangement that is said to maintain intimate surface contact and precise alignment of the shutter member relative to the image member.
With such a knowledge of the state of the art at hand, it becomes dear that a moveable display device capable of maintaining an image member and a shutter member in constantly dose contact and in exceedingly accurate registration certainly would be useful. However, a manually operated moveable display device able to maintain continuously close contact and accurate registration between an image member and a shutter member while being exceedingly simple in use, structure, and manufacture undoubtedly would represent a marked advance in the art.